The role of struvite crystals and the necrobiome in estimating the postmortem interval for forensic investigations in the UK

Forensic taphonomy is a sub-discipline of forensic anthropology and has become a focal point for research in recent years to aid in the development of decomposition models specific to the United Kingdom (UK). Research in the UK has highlighted struvite crystal precipitation as a potential preliminary method for estimating the postmortem interval (PMI). The aim of this research was to investigate the use of struvite crystals and the microbial communities that precipitate them in estimating the PMI for forensic investigations in the UK. An in vitro model was established through the development of a differential media to select and identify bacteria that allow for the formation of struvite crystals through the detection of urease enzyme activity. This successfully aided in the preliminary analysis of ureolytic bacteria by causing a statistically measurable colour change. Identification of these isolates was obtained by conducting matrix-assisted laser desorption ionisation-time-of-flight mass spectrometry (MALDI-TOF-MS). To confirm the identity of the crystals, samples were subjected to analytical tests to determine the elemental composition, molecular bonds and the morphological features. The results indicated that the samples grown from the isolates of interest and those which appeared on the surface of articular cartilage were struvite due to mirroring the features of identified struvite. An alternative method of detecting the presence of ureolytic organisms was carried out through the sampling of volatile organic compounds (VOCs) which were analysed by gas chromatography-mass spectrometry (GC-MS). VOCs were sampled in vitro from cultures to establish baseline profiles for each organism. Porcine cadavers were used in an outdoor environment; ex vivo measurements of VOCs were sampled during decomposition and compared to the in vitro bacterial profiles findings to determine whether organisms of interest could be identified. 1-Butanol, 3-methyl-, produced by Proteus spp. has been observed within the necrobiome. This provided an assessment of succession in ureolytic bacteria that suggests potential as a complimentary method for estimating the PMI. In summary, findings from this research indicate that sampling and identifying struvite crystals in forensic investigations is a time-consuming, invasive and destructive process. This suggests that this is not feasible for real-world applications where non-invasive, evidence preserving and timely approaches would be preferred. Research has also shown that the focus should be on the postmortem community of ureolytic organisms, rather than struvite as this is a byproduct of the decomposition process. Exploratory findings suggest that it likely be possible to identify ureolytic organisms within the VOCs of the necrobiome. Further research can build upon these discoveries to establish a comprehensive framework for this complimentary model.

Citation

Angell, H. (2025) The role of struvite crystals and the necrobiome in estimating the postmortem interval for forensic investigations in the UK. University of Wolverhampton. https://wlv.openrepository.com/handle/2436/626121

Publisher

University of Wolverhampton

URI

https://wlv.openrepository.com/handle/2436/626121

Type

Thesis or dissertation

Language

en

Description

A thesis submitted in partial fulfilment of the requirements of the University of Wolverhampton for the degree of Doctor of Philosophy. Content warning: Photographs of porcine cadavers in Appendix 3 and at various locations in the thesis.

Collections

Theses and Dissertations